A Luminescent Ionic Liquid Crystal: [C12mim]4[EuBr6]Br

[C(12)mim](4)[EuBr6]Br center dot CH3CN (2) was obtained at -15 degrees C by reacting europium bromide with [C(12)mim]Br (1-dodecyl-3-methylimidazolium bromide) in acetonitrile. 2 crystallizes in the triclinic space group P (1) over right arrow (No. 2) with two formula units in the unit cell. The structure is characterized by double layers of [C12mim] cations with interdigitated alkyl chains which are separated by anion layers formed by [EuBr6] octahedra and Br center dot center dot center dot CH3CN units. Upon warming to room temperature 2 looses acetonitrile to form the room temperature ionic liquid crystal [C(12)mim](4)[EuBr6]Br (1). The temperature dependent structural behavior has been characterized by differential scanning calorimentry and hot-stage polarizing optical microscopy. In the temperature range of -3 to 98 degrees C 1 adopts a smectic liquid crystal phase. At 77 K 1 shows a strong red emission with a lifetime of 2.6 ms. Analysis of the emission spectrum yields a quantum efficiency of 0.45.